Encapsulant layer for photovoltaic module, photovoltaic module and method for manufacturing regenerated photovoltaic cell and regenerated transparent front face substrate

ABSTRACT

An encapsulant layer for a photovoltaic module enabling recovering and recycling or reusing of reutilizeable resources such as a transparent front face substrate and photovoltaic cell and the like among constituents of a photovoltaic module, and a method for manufacturing a regenerated photovoltaic cell and a regenerated transparent front face substrate. The photovoltaic module is formed by laminating: a transparent front face substrate; a photovoltaic cell carrying a wiring electrode and a takeoff electrode, and an encapsulant layer is placed on at least one surface; and a rear face protecting sheet. The encapsulant layer is a separable layer formed mainly of a thermoplastic resin, and an output maintenance factor of photoelectronic power of the photovoltaic module using the encapsulant layer is in a range of 80% to 100%.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Application Serial Numbers:2003-318544, filed Sep. 10, 2003 and 2004-157847, filed May 27, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an encapsulant layer for photovoltaicmodule comprising a transparent front face substrate, photovoltaic celland a separable layer, to a method for manufacturing a regeneratedphotovoltaic cell and a regenerated transparent front face substrate andto a method for reutilizing a photovoltaic module.

2. Description of Related Art

Recently, since environmental problems are more and more concerned, asolar photovoltaic generation system as an inexhaustible and cleanenergy source attracts attention, and its amount of production isincreasing year by year.

However, for an active use of a solar photovoltaic generation system ina large scale, further significant cost down is essential. Specifically,it is required to realize a power generating cost corresponding toexisting electric power generating systems such as thermal powergeneration and the like, to reduce the energy consumed to manufacture aphotovoltaic cell and photovoltaic module, and to reduce the cost ofconstituents.

When large scale introduction of a solar photovoltaic generation systemis realized, a large scale disposal of the equivalent amount isconcerned. Under insistence of necessity of resource circulating typesociety construction, it is not desirable for the solar photovoltaicgeneration systems expected to support the future clean energy sourcesto inherit current industrial waste treating methods and to consumeresources in large amount. Therefore, it is necessary to construct arecycle system suppressing consumption of resources and reducing load onenvironments by efficient use of substances, recycle or reuse thereof.Further, it is necessary to develop a photovoltaic module enablingrealization of its recycling system.

A photovoltaic module is generally formed by sequentially laminating atransparent front face substrate, encapsulant sheet, a photovoltaiccell, encapsulant sheet and rear face protecting sheet, and these arefixed by an aluminum outer frame to give a module. A plurality of thesemodules are arranged to be a unit to give a solar photovoltaicgeneration system.

Of these constituents, a transparent front Lace substrate such as glassand the like and a photovoltaic cell are resources which show smalldamages as compared with surrounding members even exposed to solar lightfor a long period of time and which can be reutilized.

However, in many photovoltaic modules currently marketed, an EVA(ethylene-vinyl acetate copolymer resin) sheet is used as an encapsulantsheet, and since a thermo-setting EVA sheet is very difficult to beseparated from other module constituents, it is difficult to recover atransparent front face substrate and a photovoltaic cell from a usedmodule. In addition, a heat cross-linking process for a long period oftime is necessary, increasing energy amount in manufacturing a module.Further, there is a problem that an acidic gas is generated as an outgas in cross-linking which deteriorates circumferential environments,and additionally, a photovoltaic cell and electrode and the like aredamaged and deteriorated.

Prior technological literatures for the present invention have not beenfound.

SUMMARY OF THE INVENTION

The main object of the present invention is to provide an encapsulantlayer for photovoltaic module used in a photovoltaic module enablingrecovering and recycling or reusing of reutilizeable resources such as atransparent front face substrate and photovoltaic cell ard the likeamong constituents of a photovoltaic module, and to provide a method formanufacturing a regenerated photovoltaic cell and a regeneratedtransparent front face substrate, of which reutilize is particularlydesired because of high cost, among reutilizeable resources of aphotovoltaic module.

The present inventors have intensively studied in view of the abovementioned facts and resultantly found that reutilizeable resources suchas a photovoltaic cell and the like can be easily recovered from usedphotovoltaic modules, by providing a separable layer, as an encapsulantlayer, formed mainly of a thermoplastic resin, leading to completion ofthe invention.

That is, the present invention provides an encapsulant layer forphotovoltaic module, wherein the encapsulant layer for photovoltaicmodule is used in a photovoltaic module formed by laminating: atransparent front face substrate; a photovoltaic cell carrying a wiringelectrode and a takeoff electrode, and an encapsulant layer is placed onat least one surface; and a rear face protecting sheet, in this order,

comprising a separable layer formed mainly of a thermoplastic resin (a)having a peeling strength from the transparent front face substrate,measured in a 180° peeling test under a 25° C. atmosphere, in a range of1 N/15 mm width to 150 N/15 mm width, (b) having a Vicat softeningtemperature, measured based on JIS standard K7206, in a range of 60° C.to 128° C., and (c) having a melt mass flow rate, measured based on JISstandard K7210, in a range of 0.1 g/10 min to 50 g/10 min, and

wherein (d) an output maintenance factor of photoelectronic power,before and after a test measured based on a standard, of thephotovoltaic module using the encapsulant layer is in a range of 80% to100%.

In the present invention, the encapsulant layer for photovoltaic modulehas a separable layer composed mainly of a thermoplastic resin.Therefore, there is a merit that reutilizeable resources can be easilyrecovered from a used photovoltaic module. Further, in the presentinvention, a photovoltaic module using the above mentioned encapsulantlayer for photovoltaic module, because of the property as describedabove, can sufficiently satisfy properties required as a photovoltaicmodule.

In the above mentioned invention, it is preferable that the encapsulantlayer placed in between the transparent front face substrate and thephotovoltaic cell (e) has a total ray transmittance in a range of 70% to100%. The encapsulant layer placed in between the transparent front facesubstrate and the photovoltaic cell preferably has total raytransmittances in the above mentioned range, in view of power generationefficiency.

It is preferable that the above mentioned separable layer is placed soas to contact with the both surfaces of the photovoltaic cell and thetransparent front face substrate. The reason for this is that since theseparable layer is in contact with the both surfaces of the photovoltaiccell and the transparent front face substrate, the photovoltaic cell andtransparent front face substrate can be easily separated from a usedphotovoltaic module, and additionally, the encapsulant layer adhered tothe photovoltaic cell and transparent front face substrate can be easilyremoved.

In this case, the above mentioned encapsulant layer may be obtained bylaminating the separable layer, a filling layer formed of a resincomposition different from that of the separable layer, and theseparable layer, in this order. The reason for this is that in removingthe photovoltaic cell and transparent front face substrate from aphotovoltaic module, only the part of the encapsulant layer in contactwith them is required to be a filling layer.

On the other hand, in the present invention, the above mentionedencapsulant layer may be formed only of the above mentioned separablelayer. The reason for this is that since the encapsulant layer is formedonly of the separable layer, each constituent can be easily separatedfrom a used photovoltaic module, and additionally, encapsulant layersadhered to each constituent can be easily removed, consequently,reutilizeable resources such as a photovoltaic cell, transparent frontface substrate and the like can be recovered by a simpler method.

In the above mentioned invention, it is preferable that the peelingstrength between the encapsulant layer and the transparent front facesubstrate, measured in a 180° peeling test under a 25° C. atmosphere,after the photovoltaic module is left under high temperature and highhumidity conditions of 85° C. and 85% for 1000 hours is in a range of0.5 N/15 mm width to 140 N/15 mm width. The reason for this is that whenthe peeling strength from the transparent front face substrate is inthis range, it can sufficiently stand use for a long period of time.

It is preferable that such a thermoplastic resin is a copolymer of apolyethylene for polymerization and an ethylenically unsaturated silanecompound.

It is preferable that the above mentioned thermoplastic resin furthercontains a polyethylene for addition. The reason for this is that thecost for manufacturing a photovoltaic module can be suppressed.

In the above mentioned invention, it is preferable that the separablelayer contains Si (silicon) in an amount of 8 ppm to 3500 ppm in termsof polymerized Si amount. The reason for this is that by containingpolymerized Si by an amount in this range, adhesion to a photovoltaiccell, transparent front face substrate and rear face protecting sheetcan be improved.

It is preferable that the gel fraction of the above mentioned separablelayer is 30% or less. When the gel fraction is over the above mentionedrange, processability in manufacturing a photovoltaic module lowers, andimprovement in close adherence with a transparent front face substrateand rear face protecting sheet is not confirmed. Further, when the gelfraction is over the above mentioned range, it is difficult to reutilizemembers contained in the photovoltaic module, for example, aphotovoltaic cell and transparent front face substrate.

It is preferable that the separable layer used in the present inventionfurther contains at least ore additive selected from the groupconsisting of photo-stabilizers, ultraviolet absorbers,thermo-stabilizers and antioxidants. The reason for this is that bycontaining these additives, mechanical strength, prevention ofyellowing, prevention of cracking, and excellent processing proprietystable over a long period of time can be obtained.

The present invention also provides a photovoltaic module using theabove mentioned encapsulant layer for photovoltaic module.

Further, the present invention provides a method for manufacturing aregenerated photovoltaic cell, wherein a regenerated photovoltaic cellis obtained from the above mentioned photovoltaic module, comprising:

-   -   a heating process of heating the photovoltaic module at        temperatures not lower than the softening temperature of a        thermoplastic resin which is a constituent material of the        separable layer;    -   a separating process of peeling the separable layer, plasticized        by heating, to separate the photovoltaic cell; and    -   a removing process of removing the encapsulant layer adhered to        the photovoltaic cell.

In the above mentioned method, there is a merit that a regeneratedphotovoltaic cell can be easily manufactured, since a photovoltaic cellcan be easily separated from a used photovoltaic module.

It is preferable that the above mentioned removing process is carriedout by physical cleaning of physically removing the encapsulant layer,chemical cleaning of chemically removing the encapsulant layer, or acombination thereof.

Furthermore, the present invention provides a method for manufacturing aregenerated transparent front face substrate, wherein a regeneratedtransparent front face substrate is obtained from the photovoltaicmodule according to claim 12, comprising:

-   -   a heating process of heating the photovoltaic module at        temperatures not lower than the softening temperature of a        thermoplastic resin which is a constituent material of the        separable layer;    -   a separating process of peeling the separable layer, plasticized        by heating, to separate the transparent front face substrate;        and    -   a removing process of removing the encapsulant layer adhered to        the transparent front face substrate.

In the above mentioned method, there is a merit that a regeneratedtransparent front face substrate can be easily manufactured, since atransparent front face substrate can be easily separated from a usedphotovoltaic module.

It is preferable that the above mentioned removing process is carriedout by physical cleaning of physically removing the encapsulant layer,chemical cleaning of chemically removing the encapsulant layer, or acombination thereof.

The present invention also provides a method for reutilizing aphotovoltaic module, wherein a member from the photovoltaic moduleaccording to claim 12 is reutilized, comprising:

-   -   a heating process of heating the photovoltaic module at        temperatures not lower than the softening temperature of a        thermoplastic resin which is a constituent material of the        separable layer; and    -   a separating process of peeling the separable layer plasticized        by heating to separate the transparent front face substrate. In        this method, a photovoltaic cell or transparent front face        substrate can be easily reutilized (recycle or reuse).

In the above mentioned method for reutilizing a photovoltaic module, itis preferable that the separating process comprises a rear faceprotecting sheet separating process of separating a rear face protectingsheet from the photovoltaic module. For example, when a materialgenerating a harmful gas by heating such as a fluorine resin and thelike is used as the rear face protecting sheet, load on environments inreutilizing a photovoltaic module can be decreased by comprising a rearface protecting sheet separating process of separating a rear faceprotecting sheet from the above mentioned photovoltaic module.

In the encapsulant layer for photovoltaic module of the presentinvention, each constituent can be easily separated by heating thephotovoltaic module, using this encapsulant layer, at temperatures notlower than the softening temperature of a thermoplastic resin which is amain component of the separable layer. Therefore, there is a merit thatreutilizeable resources such as a photovoltaic cell and transparentfront face substrate and the like can be easily recovered from a usedphotovoltaic module. The recovered resources can be reused as they areas constituents of a photovoltaic module, or can be recycled byheat-melting to give other materials to be used. Particularly, it isuseful in that a regenerated photovoltaic cell and a regeneratedtransparent front face substrate can be easily obtained from a usedphotovoltaic module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing one example of thephotovoltaic module of the present invention.

FIG. 2 is a schematic sectional view showing one example of theseparation device used in a method for manufacturing regeneratedphotovoltaic cell of the present invention.

FIG. 3 is a diagrammatic perspective vies showing one example of theseparation device used in a method for manufacturing regeneratedphotovoltaic cell of the present invention.

DESCRIPTION OR THE PREFERRED EMBODIMENTS

The present invention includes an encapsulant layer for photovoltaicmodule, a photovoltaic module using the same, and a method formanufacturing a regenerated photovoltaic cell and regeneratedtransparent front face substrate, further, a method for reutilizing aphotovoltaic module. These will be explained in detail below.

A. Encapsulant Layer for Photovoltaic Module

The encapsulant layer for photovoltaic module of the present inventionis an encapsulant layer for photovoltaic module, wherein the encapsulantlayer for photovoltaic module is used in a photovoltaic module formed bylaminating: a transparent front face substrate; a photovoltaic cellcarrying a wiring electrode and a takeoff electrode, and an encapsulantlayer is placed on at least one surface; and a rear face protectingsheet, in this order,

-   -   comprising a separable layer formed mainly of a thermoplastic        resin (a) having a peeling strength from the transparent front        face substrate, measured in a 180° peeling test under a 25° C.        atmosphere, in a range of 1 N/15 mm width to 150 N/15 mm        width, (b) having a Vicat softening temperature, measured based        on JIS standard K7206, in a range of 60° C. to 128° C., and (c)        having a melt mass flow rate, measured based on JIS standard        K7210, in a range of 0.1 g/10 min to 50 g/10 min, and    -   wherein (d) an output maintenance factor of photoelectronic        power, before and after a test measured based on a standard, of        the photovoltaic module using the encapsulant layer is in a        range of 80% to 100%.

The constitution of a photovoltaic module using an encapsulant layer forphotovoltaic module of the present invention will be explained referringto a drawing. FIG. 1 is a schematic sectional view showing one examplesof such photovoltaic module. A plurality of the photovoltaic cells 1 isarranged in the same plane. And in between the photovoltaic cells, thewiring electrodes 2 and the takeoff electrodes 3 are placed. Thephotovoltaic cell 1 is sandwiched between an upper encapsulant layer 4 aand a lower encapsulant layer 4 b, and the transparent front facesubstrate 5 is laminated on the outside of the upper encapsulant layer 4a, and the rear face protecting sheet 6 is laminated on the outside ofthe lower encapsulant layer 4 b. This photovoltaic module 10 may befixed by the outer frame 7 formed of aluminum and the like. Anencapsulant layer for photovoltaic module used in such photovoltaicmodule will be described below.

the encapsulant layer of the present invention is an adhesive protectingsheet for directly fixing a photovoltaic cell and other circumferentialwirings, and has a function to adhere to a transparent front facesubstrate or to a rear face protecting sheet.

In the present invention, the above mentioned encapsulant layer may beplaced on at least one surface of the photovoltaic cell as describedabove, however, a configuration, in which the encapsulant layers areplaced on both surfaces of the photovoltaic cell and sandwich thephotovoltaic cell, is preferable.

It is necessary that the encapsulant layer used in the photovoltaicmodule of the present invention satisfies the following condition (a)for sufficing required properties of a photovoltaic module.

(a) Close Adherence to Transparent Front Face Substrate

The encapsulant layer for photovoltaic module of the present inventionplays a role to adhere the photovoltaic cell to the transparent frontface substrate. Therefore, high close adherence between the encapsulantlayer and transparent front face substrate is necessary.

In the present invention, a peeling strength of the encapsulant layerfrom the transparent front face substrate, which is measured in a 180°peeling test under 25° C. atmosphere, is in a range of 1 N/15 mm widthto 150 N/15 mm width, preferably in a range of 3 N/15 mm width to 150N/15 mm width, more preferably in a range of 10 N/15 mm width to 150N/15 mm width.

The above mentioned peeling strength is a value obtained by thefollowing test method.

-   -   Testing machine: Tensile testing machine manufactured by A & D        Co., LTD, [machine name; Tensilon]    -   Measuring angle: 180° peeing    -   Peeling speed: 50 mm/min

Within this range, close adherence between the transparent front facesubstrate and the encapsulant layer is sufficient, and generation ofvoids at the adhesion interface thereof can be suppressed.

The encapsulant layer used in the present invention preferably has theabove mentioned property for a long period of time, and the peelingstrength between the encapsulant layer and the transparent front facesubstrate, measured in a 180° peeling test under a 25° C. atmosphere,after the above mentioned photovoltaic module being left for 1000 hoursunder high temperature and high humidity conditions of 85° C. and 85% ispreferably in a range of 0.5 N/15 mm width to 140 N/15 mm width, morepreferably in a range of 3 N/15 mm width to 140 N/15 mm width, furtherpreferably in a range of 10 N/15 mm width to 140 N/15 mm width. As themeasuring method, the sane method as described above is used.

The encapsulant layer for photovoltaic module of the present invention,when placed in between the transparent front face substrate and thephotovoltaic cell, preferably has a property (e) as described below.

(e) Ray Transmittance

The encapsulant layer used in between the transparent front facesubstrate and the photovoltaic cell is required to have high raytransmittance. In the present invention, the total ray transmittance ofan encapsulant layer is in a range of 70% to 100%, preferably 80% to100%, more preferably 90% to 130%.

The total ray transmittance can be measured by a usual method, and forexample, it can be measured by a color computer.

The encapsulant layer used in between the rear face protecting sheet andthe photovoltaic cell is not particularly required to have total raytransmittance as described above, and rather, this encapsulant layer ispreferably an encapsulant layer colored by filling an inorganic pigment,for design and improvement in power generation efficiency by reflectinglight.

The encapsulant layer used in the present invention satisfies therequired property as described above, and has the separable layer mainlyformed of a thermoplastic resin.

In the photovoltaic nodule of the present invention, the encapsulantlayer is preferably constituted only of the separable layer, and mayalso have a multi-layered structure with the separable layer and thefilling layer which is formed of a resin composition which is differentfrom that of the separable layer.

When the encapsulant layer is constituted only of the separable layer,each constituent can be easily separated from a used photovoltaicmodule, and in addition, the encapsulant layer adhered to eachconstituent can be removed easily, therefore, it is advantageous in thatreutilizeable resources such as the transparent front face substrate andphotovoltaic cell and the like can be recovered by a simpler method.

On the other hand, in the case of a multi-layered structure, theconstitution is not particularly limited as long as it is constituted ofthe separable layer and the filling layer, and for example,constitutions such as a two-layered structure composed of the separablelayer and the filling layer, a three-layered structure obtained bylaminating the separable layer, the filling layer and the separablelayer in this order, and the like can be presented. By thus using afilling layer, the using amount of a relatively expensive separablelayer material can be reduced. Therefore, it is advantageous from thestandpoint of the cost.

When the encapsulant layer has a multi-layered structure, in thephotovoltaic module of the present invention, it is preferable thatseparable layers are placed so as to contact with the both surfaces ofthe photovoltaic cell and the transparent front face substrate. Thereason for this is that when separable layers are placed so as tocontact with the photovoltaic cell and the transparent front facesubstrate, separable layers can be plasticized by heating, consequently,the photovoltaic cell and the transparent front face substrate can beeasily removed, additionally, separable layers adhered to thephotovoltaic cell and the transparent front face substrate can be easilyremoved. Thus recovered photovoltaic cell and transparent front facesubstrate can be reutilized as a regenerated photovoltaic cell andregenerated transparent front face substrate.

Therefore, when the encapsulant layer has a multi-layered structure, athree-layered structure obtained by laminating the above mentionedseparable layer, filling layer and separable layer in this order isparticularly preferable.

Even if the filling layer is placed in contact with the photovoltaiccell, the amount of the filling layer adhered to the photovoltaic cellcan be decreased by selecting the material of the filling layer.Therefore, this is useful, for example, in that a regeneratedphotovoltaic cell can be obtained by chemical cleaning and the like.Moreover when the filling layer is placed in contact with thetransparent front face substrate, the filling layer adhered can beremoved by chemical cleaning and reused, and the amount of the adheredsubstance can be suppressed low, so that recycling becomes possible byheat-melting.

The separable layer and filling layer will be described below.

(1) Separable Layer

The separable layer is, as described above, a layer mainly formed of athermoplastic resin. Here, “mainly formed of” means that the separablelayer material contains a thermoplastic resin in an amount of 50 wt % ormore, preferably 70 wt % or more, more preferably 90 wt % or more.

In the present invention, since the encapsulant layer has a separablelayer mainly formed of a thermoplastic resin, the separable layer can beplasticized by heating at temperatures not lower than the softeningtemperature of the thermoplastic resin, the separable layer can bepeeled and reutilizeable resources such as the photovoltaic cell and thelike can be easily recovered and reused or recycled.

It is necessary that such the thermoplastic resin (b) has a Vicatsoftening temperature, measured based on JIS standard K7206, in a rangeof 60° C. to 128° C., preferably from 60° C. to 110° C., furtherpreferably from 60° C. to 110° C.

Since the thermoplastic resin has a softening temperature in this range,the separable layer can be easily plasticized without damaging otherconstituents of the photovoltaic module.

The thermoplastic resin used in the present invention (c) has a meltmass flow rate, measured based on JIS standard K7210, in a range of 0.1g/10 min to 50 g/10 min, preferably from 0.1 g/10 min to 10 g/10 min,more preferably from 0.5 g/10 min to 8 g/10 min.

Within this range, the flowability of the thermoplastic resin inmanufacturing the photovoltaic module is suitable, therefore,processability is excellent, and additionally, when the separable layerand other constituents such as the transparent front face substrate andthe like are laminated so that they directly come into mutual contact,close adherence at the interface is secured sufficiently.

Further, the thermoplastic resin used in the present invention ispreferably a resin revealing no yellowing even if exposed to solar rayfor a long period of time. Specifically, the degree of yellowingmeasured based on JIS standard K7105 is preferably 50% increase or less,more preferably 25% increase or less, further preferably 5% increase orless.

The thermoplastic resin which is a material of the separable layer, andother additives will be explained specifically below.

(Thermoplastic Resin)

The thermoplastic resin used in the present invention is notparticularly limited as long as it satisfies the above mentionedrequired property, and for example, a copolymer of a polyethylene forpolymerization and an ethylenically unsaturated silane compound ismentioned as a preferable example.

In the present invention, the copolymer may be any of a randomcopolymer, alternative copolymer, block copolymer and graft copolymer.Among them, particularly when close adherence with other constituentssuch as the transparent front face substrate and the like is necessary,a graft copolymer is preferable, and in the case of a graft copolymer, asilane-modified resin, wherein an ethylenically unsaturated silanecompound is arranged as a side chain on a main chain of a polyethylenefor polymerization, is preferable.

The polyethylene for polymerization used in the present invention is notparticularly limited as long as it is a polyethylene-based polymer, andspecifically, low density polyethylene, middle density polyethylene,high density polyethylene, super low density polyethylene, ultra superlow density polyethylene and straight chain low density polyethylene arepreferable. These can be used singly or in combination of two or more.

Further, the above mentioned polyethylene for polymerization ispreferably a polyethylene having many side chains. Usually, apolyethylene having many side chains has low density, and a polyethylenehaving a small number of side chains has high density. Therefore, apolyethylene of low density is preferable. In the present invention, thedensity of a polyethylene for polymerization is preferably in a range of0.850 to 0.960 g/cm³, more preferably in a range of 0.865 to 0.930g/cm³. The reason for this is that when the polyethylene forpolymerization is a polyethylene having many side chains, namely, apolyethylene of low density, there is a tendency that an ethylenicallyunsaturated silane compound is graft-polymerized to a polyethylene forpolymerization.

On the other hand, the ethylenically unsaturated silane compound used inthe present invention is not particularly limited, and preferable is atleast one selected from the group consisting of vinyltrimethoxysilane,vinyltriethoxysilane, vinyltripropoxysilane, vinyltributoxysilane,vinyltripentyloxysilane, vinyltriphenoxysilane, vinyltribenzyloxysilanervinyltrimethylenedioxysilane, vinyltriethylenedioxysilane,vinylpropionyloxysilane, vinyltriacetoxysilane andvinyltricarboxysilane.

The method for manufacturing the above mentioned copolymer is notparticularly limited, and the above mentioned copolymer can besynthesized by a usual method. For example, the copolymer can beobtained by mixing the above mentioned polyethylene for polymerization,the above mentioned ethylenically unsaturated silane compound and acatalyst and polymerizing them at high temperatures. In this procedure,the heating temperature is preferably 300° C. or less, more preferably270° C. or less. The reason for this is that when the temperature ishigher than this, a silanol group portion tends to be cross-linked to bea gel.

Particularly in the case of obtaining a graft copolymer, copolymer canbe obtained by mixing and heat-melting a polyethylene forpolymerization, ethylenically unsaturated silane compound and freeradical generator. Preferable heating temperature is the same asdescribed above.

Examples of free radical generator include: hydroperoxides such asdiisopropylbenzene hydroperoxide, 2,5-dimethyl-2,5-di(hydroperoxy)hexaneand the like; dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane-3 and the like;diacyl peroxides such as bis-3,5,5-trimethyl hexanyl peroxide, octanoylperoxide, benzoyl peroxide, o-methylbenzoyl peroxide,2,4-dichlorobenzoyl peroxide and the like; peroxy esters such ast-butyl-peroxy isobutyrate, t-butyl peroxy cyanate, t-butylperoxy-2-ethyl hexanoate, t-butyl peroxy pivalate, t-butyl peroxyoctoate, t-butyl peroxy isopropyl carbonate, t-butyl peroxy benzoate,di-t-butyl peroxy phthalate, 2,5-dimethyl-2,5-di(benzoyl peroxy)hexane,2,5-dimethyl-2,5-di(benzoyl peroxy)hexane-3 and the like; organicperoxides such as ketone peroxides such as methyl ethyl ketone peroxide,cyclohexanone peroxide and the like, or azo compounds such asazobisisobutyronitrile, azobis(2,4-dimethylvaleronitrile) and the like.

The using amount of the free radical generator is preferably 0.001 wt %or more in the above mentioned silane-modified resin.

In the above mentioned copolymer, the using amount of an ethylenicallyunsaturated silane compound is preferably in a range of 0.001 parts byweight to 4 parts by weight, more preferably in a range of 0.01 parts byweight to 3 parts by weight, based on 100 parts by weight of apolyethylene for polymerization.

It is preferable that the thermoplastic resin used in the presentinvention further contains a polyethylene for addition in addition tothe above mentioned copolymer. The reason for this is that since theabove mentioned copolymer is expensive, it is more advantageous, fromthe standpoint of cost, to form the separable layer by mixing thepolyethylene for addition than to form the separable layer only with thecopolymer.

The polyethylene for addition used in the present invention ispreferably at least one selected from the group consisting of lowdensity polyethylene, middle density polyethylene, high densitypolyethylene, super low density polyethylene, and straight chain lowdensity polyethylene.

The content of the polyethylene for addition is preferably in a range of0.01 parts by weight to 9900 parts by weight, more preferably in a rangeof 90 parts by weight to 9900 parts by weight, based on 100 parts byweight of the above mentioned copolymer.

When two or more of the above mentioned copolymers are utilized, it ispreferable that the content of the polyethylene for addition is in theabove mentioned range based on 100 parts by weight of the total amountthereof.

(Other Additives)

As the material of the separable layer, it is preferable that at leastone additive selected from the group consisting of photo-stabilizers,ultraviolet absorbers, thermo-stabilizer and antioxidants is furthercontained. The reason for this is that by inclusion of these additives,mechanical strength, prevention of yellowing, prevention of cracking andexcellent processing propriety stable over a long period of time can beobtained.

The photo-stabilizer arrests an active species, which initiates lightdeterioration, in the thermoplastic resin used in the separable layerand prevents photo oxidation. Specifically, photo-stabilizers such ashindered amine-based compounds, hindered piperidine compounds and thelike can be listed.

The ultraviolet absorber absorbs harmful ultraviolet ray in solar light,converts the ray into harmless thermal energy in the molecule, andprevents excitation of an active species, which initiates lightdeterioration, in the thermoplastic resin used in the separable layer.Specifically, inorganic ultraviolet absorbers such as benzophenone-basedabsorbers, benzotriazole-based absorbers, salicylate-based absorbers,acrylonitrile-based absorbers, metal complex salt-based absorbers,hindered amine-based absorbers, ultra fine particle titanium oxide(particle size: 0.01 μm to 0.06 μm), or ultra fine particle zinc oxide(particle size: 0.01 m to 0.04 μm) and the like can be listed.

As the thermo-stabilizer: phosphorus-based thermo-stabilizers such astris(2,4-di-t-butylphenyl) phosphate, vis[2,4-bis(1,1-dimethylethyl)-6-methylphenyl]ethyl phosphite,tetrakis(2,4-di-t-butylphenyl) [1,1-biphenyl]-4,4′-diyl bisphosphonite,bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite and the like;lactone-based thermo-stabilizers such as a reaction product of8-hydroxy-5,7-di-t-butyl-furan-2-one with o-xylene, and the like can belisted. It is preferable to use a phosphorus-based thermo-stabilizer anda lactone-based thermo-stabilizer together.

The antioxidant prevents deterioration by oxidation of a thermoplasticresin used in the separable layer. Specific examples thereof includephenol-based, amine-based, sulfur-based, phosphorus-based, lactone-basedantioxidants and the like.

These photo-stabilizers, ultraviolet absorbers, thermo-stabilizers andantioxidants can be used singly or in combination of two or more.

The content of photo-stabilizers, ultraviolet absorbers,thermo-stabilizers and antioxidants differs depending on its particleshape, density and the like, and preferably in a range of 0.001 wt % to5 wt % based on materials in the separable layer.

(Separable Layer)

In the present invention, it is preferable that Si (silicon) iscontained in the above mentioned separable layer, in an amount in arange of 8 ppm to 3500 ppm, particularly 10 ppm to 3000 ppm, moreparticularly 50 ppm to 2000 ppm, in terms of polymerized Si amount. Thereason for this is that when polymerized Si amount is in this range,close adherence with the transparent front face substrate or thephotovoltaic cell can be kept excellent.

In the present invention, as a method for measuring polymerized Siamount, there is used a method in which only an encapsulant layer isheated, burnt and ashed, consequently, polymerized Si is converted intoSiO₂, and the ash is melted in an alkali and dissolved in pure water,then, its volume was controlled into a constant volume and polymerizedSi amount was quantified by an ICP emission analysis (high frequencyplasma emission analysis apparatus: manufactured by ShimadzuCorporation, ICPS8100) method.

It is preferable that the gel fraction of the separable layer used inthe photovoltaic module of the present invention is 30% or less,particularly 10% or less, more particularly 0%. When the gel fraction isover the above mentioned range, processability in manufacturing thephotovoltaic module lowers, and improvement in close adherence with thetransparent front face substrate and rear face protecting sheet is notrecognized. Further, when the gel fraction is over the above mentionedrange, it is difficult to reutilize members contained in thephotovoltaic module, for example, the photovoltaic cell and thetransparent front face substrate.

The gel fraction of the separable layer in the present invention means agel fraction of the separable layer when a photovoltaic module ismanufactured, by using usual molding methods such as a lamination methodin which layers such as transparent front face substrate, encapsulantlayer, photovoltaic cell, encapsulant layer and rear face protectingsheet are laminated in this order, and then, these are made into anintegrated molded body, vacuum-sucked and thermocompressed as anintegrated body.

In such a method for measuring gel fraction; 1 g of the encapsulantlayer for photovoltaic module is weighed and placed in a 80 mesh wiregauze bag; the sample is placed together with the wire gauze into aSoxhlet extractor, and xylene is refluxed under its boiling point; aftercontinuous extraction for 24 hours, the sample is removed together withthe wire gauze, dried, then, weighed, and the weight before extractionand the weight after extraction is compared and wt % of remaininginsoluble components is measured as a gel fraction.

In the separable layer used in the present invention, although it is notparticularly limited, a silanol condensation catalyst promoting adehydration condensation reaction between silanols of silicone, such asdibutyltin diacetate, dibutyltin dilaurate, dibutyltin dioctaze anddioctyltin dilaurate may be added in the separable layer by an amount of0.05 parts by weight or less based on 100 parts by weight of athermoplastic resin, to obtain the above mentioned gel fraction.However, it is preferable that the above catalyst is not added.

(2) Filling Layer

Next, the filling layer will be explained. As described above, thefilling layer is formed of a resin composition different from that ofthe separable layer, and is not particularly limited as long as it isdesirably formed of a resin composition cheaper than that of theseparable layer. For example, it is also possible to use resins showingno change of plasticity even when heated at temperatures plasticizingthe above mentioned separable layer, for example, cross-linkable resinssuch as a cross linking agent added EVA.

The thermo-setting resin is not particularly limited as long as itsprocessability is excellent and adhesion to other constituents such asthe transparent front face substrate, rear face protecting sheet and thelike is excellent. Known thermosetting resins conventionally used as theencapsulant layer can be used. The filling layer can also containvarious additives intending an improvement of mechanical strength,prevention of yellowing, and prevention of cracking and the like.

When the separable layer contains a copolymer of a polyethylene forpolymerization with an ethylenically unsaturated silane compound asdescribed above, and a polyethylene for addition, it is also possiblethat the filling layer is formed of a polyethylene. The reason for thisis that, in this case, adhesion with the separable layer is excellent,and it is advantageous in view of the cost.

(3) Encapsulant Layer

The thickness of the encapsulant layer for photovoltaic module of thepresent invention is preferably in a range of 10 to 2000 μm,particularly in a range of 100 to 1250 μm. When thinner than the abovementioned range, a cell cannot be supported and the cell tends to bedamaged, and when thicker than the above mentioned range, the weight ofthe module increases and workability when installing thereof and thelike is poor, and disadvantageous in view of the cost, in some cases.

The method for manufacturing the encapsulant layer is not particularlylimited. For example, when an encapsulant layer is constituted only ofthe separable layer, the above mentioned copolymers as the thermoplasticresin can be heat-melted and extrusion-processed. It is also possiblethat a polyolefin and additives, used if necessary, in addition to theabove mentioned copolymer are mixed and placed into a hopper of anextruder, and heat-melted in a cylinder.

The heating temperature in heat-melting is preferably 300° C. or less,more preferably 270° C. or less. The reason for this is, as describedabove, that the above mentioned copolymer tends to be gelled bycross-linking of a silanol group part by heating.

After heat melting, it can be molded into a sheet having predeterminedthickness by existing methods such as T die, inflation and the like, togive an encapsulant layer used in the photovoltaic module of the presentinvention.

On the other hand, when the encapsulant layer has a multi-structure, itcan be manufactured as an integrated molded body is possible by, forexample, a lamination method and the like in which the separable layerand the filling layer are previously molded into a sheet, and integratedby vacuum-sucked and the like and thermocompressed as described above.

(4) Photovoltaic Module

A photovoltaic module using the encapsulant layer for photovoltaicmodule of the present invention as described above is required to havehigh maintenance factor of conversion efficiency for standing use for along period of time.

For this reason, in the present invention, (d) an output maintenancefactor of photoelectronic power, before and after a test measured basedon a standard, of a photovoltaic module is in a range of 80% to 100%,preferably in a range of 90% to 100%, more preferably in a range of 95%to 100%. The reason for this is that when the output maintenance factorof photoelectronic power is in this range, the maintenance factor ofconversion efficiency is secured sufficiently.

The output maintenance factor of photoelectronic power before and aftera test measured based on a standard of the photovoltaic module is, whenthe photovoltaic cell is a crystalline element, it is measured by JISstandard C8917 and when the photovoltaic cell is an amorphous element,it is measured by JIS standard C8938, and regarding other photovoltaiccells, the output maintenance factor is measured by a method pursuant tothe above.

B. Photovoltaic Module

Hereinafter, the photovoltaic module of the present invention will bedescribed. The photovoltaic module of the present invention ischaracterized in that the encapsulant layer for photovoltaic moduledescribed in the above mentioned “A. Encapsulant layer for photovoltaicmodule” is used.

Members constituting the photovoltaic module of the present inventionwill be described below. Since the encapsulant layer is the same asdescribed in the above mentioned “A. Encapsulant layer for photovoltaicmodule”, description thereof is omitted.

(1) Photovoltaic Cell

The photovoltaic cell used in the present invention is not particularlylimited as long as it has a function of photoelectronic power, and knownelements generally used as the photovoltaic cell can be used. Examplesthereof include crystalline silicone photovoltaic cells such as a singlecrystalline silicon type photovoltaic cell, polycrystalline silicon typephotovoltaic cell and the like, amorphous silicone photovoltaic cells ofsingle bonding type or tandem structure type, III-V group compound semiconductor photovoltaic cells such as gallium arsenic (GaAs), indiumphosphorus (InP) and the like, II-VI group compound semiconductorphotovoltaic cells such as cadmium tellurium (CdTe), copper indiumselenite (CuInSe₂) and the like.

Further, thin film polycrystalline silicone photovoltaic cells, thinfilm fine-crystalline silicone photovoltaic cells, hybrid elements of athin film crystalline silicon photovoltaic cell with an amorphoussilicon photovoltaic cell, and the like can also be used.

In these photovoltaic cells, an electromotive part of crystallinesilicon of p-n junction structure and the like, amorphous silicon ofp-i-n junction structure and the like or compound semiconductor and thelike is formed on a substrate such as a glass substrate, plasticsubstrate, metal substrate and the like.

In the photovoltaic module of the present invention, a plurality of thephotovoltaic cells 1 are arranged as shown in FIG. 1. In this mechanism,when this photovoltaic cell 1 is illuminated with solar light, anelectron (−) and hole (+) are generated, and electric current flowsthrough wiring electrodes 2 and takeoff electrodes 3 placed in betweenphotovoltaic cells.

(2) Transparent Front Face Substrate

In the present invention, the transparent front face substrate has afunction of protecting inside of a module from wind and weather, outerimpact, fire and the like and of securing reliability for a long periodof time of the photovoltaic module when exposed outdoors.

Such a transparent front face substrate is not particularly limited aslong as it has transmittance of solar light, electric insulationproperty, and is excellent in mechanical, chemical or physical strength,and known substrates generally used as a transparent front facesubstrate for a photovoltaic module can be used. For example, glassplates, fluorine-based resin sheets, cyclic polyolefin-based resinsheets, polycarbonate-based resin sheets, poly(meth)acrylic based-resinsheets, polyamide-based resin sheets, or polyester-based resin sheetsand the like can be listed. Particularly, it is preferable that theglass plates are utilized as the transparent front face substrate in thepresent invention. The reason for this is that a glass plate isexcellent in heat resistance. Therefore, reusing or recycling thereofwill be easy since the heating temperature, when constituents areseparated from a used photovoltaic module and the encapsulant layeradhered on the surface of the glass plate is removed, can be setsufficiently high.

(3) Rear Face Protecting Sheet

The rear face protecting sheet is a weather-resistant film protectingthe rear face of the photovoltaic module from the surrounding. As therear face protecting sheet used in the photovoltaic module of thepresent invention, metal plates or metal foils of aluminum and the like,fluorine-based resin sheets, cyclic polyolefin-based resin sheets,polycarbonate-based resin sheets, poly(meth)acrylic-based resin sheets,polyamide-based resin sheets, polyester-based resin sheets, or complexsheets obtained by laminating a weather-resistant film and a barrierfilm and the like can be listed.

The thickness of the rear face protecting sheet used in the presentinvention is preferably in a range of from 20 μm to 500 μm, morepreferably in a range of 60 μm to 150 μm.

(4) Other Constituent Member

In the present invention, other layers may further be optionallylaminated in purpose of improving a solar light absorbing property,reinforcement and other objects, in addition to the above mentionedmatters.

After laminating each constituent, an outer frame can also be providedfor fixing layers as an integrated molded body. As the outer frame,those formed of the same material as that used for the above mentionedrear face protecting sheet can be used.

(5) Method for Manufacturing Photovoltaic Module

A method for manufacturing such the photovoltaic module of the presentinvention is not particularly limited, and known methods conventionallyused as a method for manufacturing a photovoltaic module can be used.For example, by using usual forming method such as lamination method, inwhich transparent front Lace substrate, encapsulant layer, photovoltaiccell, encapsulant layer and rear face protecting sheet are laminated inthis order facing to each other, further laminating other constituentsif necessary, and then, these integrated by vacuum suction andthermocompressed, and these are molded by thermocompression as anintegrated molded body.

In the present invention, laminating temperature, when such a laminationmethod is used, is preferably in a range of 9000 to 230° C.,particularly preferably in a range of 110° C. to 190° C. When thetemperature is lower than the above mentioned range, there is apossibility that sufficient melting is not obtained and close adherencewith the transparent front face substrate, auxiliary electrode,photovoltaic cell and rear face protecting sheet and the like may bedeteriorated, and when the temperature is higher than the abovementioned range, there is a possibility that water-crosslinking due towater vapor in air tends to progress and gel fraction may be increased,which is not desirable. The laminating time is preferably in a range of5 to 60 minutes, particularly preferably in a range of 8 to 40 minutes.When time is shorter than the above mentioned range, there is apossibility that sufficient melting is not obtained and close adherencewith the above mentioned members may be deteriorated, and when time islonger than the above mentioned range, a process problem may occur,particularly, depending on temperature and humidity conditions, gelfraction may be increased. Regarding humidity, when humidity is toohigh, gel fraction may be increased, and when humidity is too low, thereis a possibility of decrease in close adherence with various members,however, at humidity under usual atmospheric environment, noparticularly problems will occur.

It is also possible that two or more layers are previously integrated bya lamination method and the like. For example, integrated layers of thetransparent front Lace substrate and the encapsulant layer, or theencapsulant layer and the rear face protecting sheet may be used.

For enhancing adhesion between layers, adhesives such as heat meltingtype adhesives, photo-curing type adhesives and the like formed mainlyof a vehicle such as a (meth) acrylic resin, olefin-based resin,vinyl-based resin and the like can be used if necessary.

Further, respective facing surfaces between laminates can be subjectedto a pre-treatment such as a corona discharge treatment, ozonetreatment, low temperature plasma treatment using an oxygen gas,nitrogen gas and the like, glow discharge treatment, oxidation treatmentusing chemicals and the like.

It is also possible that a primer coat agent layer, under coat agentlayer, adhesive layer or anchor coat agent layer and the like ispreviously formed on respective facing surfaces between laminates and asurface pretreatment may be conducted.

An outer frame for fixing an integrated body obtained by laminatingthese layers can be mounted after lamination of layers and beforeadhering under thermocompression, or may also be mounted after adheringunder thermocompression.

C. Method for Manufacturing Regenerated Photovoltaic Cell

Next, the method for manufacturing a regenerated photovoltaic cell ofthe present invention will be explained below.

The method for manufacturing a regenerated photovoltaic cell of thepresent invention is a method for manufacturing a regeneratedphotovoltaic cell, wherein a regenerated photovoltaic cell is obtainedfrom the above mentioned photovoltaic module, comprising;

-   -   a heating process of heating the photovoltaic module at        temperatures not lower than the softening temperature of a        thermoplastic resin which is a constituent material of the        separable layer;    -   a separating process of peeling the separable layer, plasticized        by heating, to separate the photovoltaic cell; and    -   a removing process of removing the encapsulant layer adhered to        the photovoltaic cell. These each process will be described        below.        1. Heating Process

In the heating process, the photovoltaic module is heated attemperatures not lower than the softening temperature of thethermoplastic resin which is a constituent material of the separablelayer. By heating at temperatures not lower than the softeningtemperature of the thermoplastic resin, the plasticity of athermoplastic resin which is a constituent material of the separablelayer changes, and the separable layer can be easily peeled.

As the heating method, a method in which the photovoltaic module isplaced in a vessel filled with a heated gas, liquid or solid such as apowder and the like or a combination thereof, a method in which thephotovoltaic module is retained on a heated hot plate, and the like canbe listed.

The heating temperature is a temperature not lower than the softeningtemperature of the thermoplastic resin which is a constituent materialof the separable layer, and appropriately selected depending on thethermoplastic resin used. Here, the softening temperature means a Vicatsoftening temperature measured based on JIS standard K7206 of the abovementioned thermoplastic resin. The heating temperature in the heatingprocess is the same as this Vicat softening temperature or higher thanthe Vicat softening temperature preferably by 0 to 390° C., morepreferably by 10 to 290° C., further preferably by 20 to 140° C.

The specific heating temperature in the above mentioned heating processis preferably in a range of 60 to 450° C., more preferably in a range of70 to 350° C., further preferably in a range of 80 to 200° C.

2. Separating Process

In the separating process in the present invention, the separable layerplasticized by heating in the above mentioned heating process is peeledto separate the photovoltaic cell. The photovoltaic cell may beseparated by any method as long as it is separated without beingdamaged.

As the separating method, a method using a separating means, a methodapplying shear stress, and the like can be listed.

The method using a separating means is a method in which the encapsulantlayer placed in between the transparent front face substrate and thephotovoltaic cell, and the encapsulant layer placed in between thephotovoltaic cell and the rear face protecting sheet, of thephotovoltaic module heated in the above mentioned heating process, arecut by making a separating means go through them, to separate thetransparent front face substrate and the rear face protecting sheet fromthe photovoltaic cell. And such a separating means is not particularlylimited as long as it can cut the encapsulant layer in softenedcondition, and wire and the like can be listed as preferable examples.The separating means using wire will be explained referring to adrawing. For example, as shown in FIG. 2, By using separation devicecomprising a jig 21 for fixed wire, a jig 22 for fixing module, and anoil bath 23, a photovoltaic cell 1 and encapsulant layer 4 are separatedby cutting of wire 24. Also, FIG. 3 is a diagrammatic perspective viewof the separation device.

The method for applying shearing force is a method in which at least oneof the photovoltaic cell of a photovoltaic module heated in the abovementioned heating process and the transparent front face substrate, orat least one of the photovoltaic cell and the rear face protectingsheet, is pushed toward transverse direction to apply shearing force tothe encapsulant layer. Thereby, the transparent front face substrate andthe rear face protecting sheet are separated from the photovoltaic cell,

3. Removing Process

In the removing process of the present invention, the encapsulant layeradhered to the photovoltaic cell is removed. As this removing method,physical cleaning of physically removing the encapsulant layer, chemicalcleaning of chemically removing the encapsulant layer, a combinationthereof and the like can be listed. Further, the encapsulant layer maybe removed by a method of combination of a plurality of chemicalcleaning methods, combination of a plurality of physical cleaningmethods, further, combination thereof.

As the above mentioned physical cleaning, a method in which a gas,liquid or solid or a combination thereof is sprayed, a method of wipingwith cloth and the like can be listed. The physical cleaning ispreferably conducted under heating of the encapsulant layer. Forexample, an air blast method and a shot blast method, in which steelsphere shots are sprayed at high speed using compressed air orcentrifugal force in a heated atmosphere and the like can be listed.When an adhered substance is a part corresponding to the separablelayer, physical cleaning is useful.

In this physical cleaning, it is necessary to remove an adheredsubstance so that the regenerated photovoltaic cell is not damaged.Therefore, for example, when the encapsulant layer is removed byspraying fine particles, the particle size of fine particles ispreferably in a range of 5 μm to 500 μm. For example, as solid which canbe used for physical cleaning, steel-based abrasive materials, stainlessabrasive materials, zinc abrasive materials, copper abrasive materials,alumina abrasive materials, silicon carbide abrasive materials, glassabrasive materials, resin abrasive materials, silica sand, ceramicbeads, zirconia, slag, calcium carbonate, sodium bicarbonate and thelike can be listed.

As the liquid, for example, heated organic solvents, metal liquid andthe like can be listed.

As the gas, air, inert gases such as nitrogen gas, argon gas, helium gasand the like can be listed.

As the chemical cleaning, a method of treating with an acid or alkali, amethod of eluting by a solvent and the like, can be listed. The solventwhich can be used for chemical cleaning can be appropriately selecteddepending on the encapsulant layer adhered.

Specifically, a method in which the separated photovoltaic cell isimmersed in an organic solvent such as xylene and the like, and theseparable layer is removed from the surface of the photovoltaic cell,and other methods can be listed. There are cases where an organicsolvent such as xylene and the like is heated or refluxed.

There are also a method in which stearic acid is poured onto theseparated photovoltaic cell under heated condition, and the separablelayer is removed, and other methods.

There are also a method in which stearic acid is poured onto theseparated photovoltaic cell under heated condition, and the encapsulantlayer is removed to a certain extent, then, the photovoltaic cellcarrying the remaining encapsulant layer on its surface is immersed inan organic solvent such as xylene and the like, and the encapsulantlayer remaining on the surface of the photovoltaic cell is peeled, andother methods. There are cases where an organic solvent such as xyleneand the like is heated or refluxed.

Further, a method can also be listed, in which the separatedphotovoltaic cell is immersed in an organic solvent such as xylene andthe like, the encapsulant layer is removed from the surface of thephotovoltaic cell to a certain extent, then, the photovoltaic cellcarrying the remaining encapsulant layer on its surface is taken out,stearic acid is poured onto, this under heated condition, and theencapsulant layer remaining on the surface of the photovoltaic cell ispeeled, and other methods. There are cases where an organic solvent suchas xylene and the like is heated or refluxed.

As the method of combining physical cleaning with chemical cleaning, forexample, methods can be listed, in which an adhered substance isimmersed to a certain extent in liquid for dissolution, then, theadhered substance is completely removed by an air blast method or shotblast method and the like.

As described above, the adhered substance can be removed, and ifnecessary, by cleaning with alcohol and the like, a regeneratedphotovoltaic cell can be easily manufactured from a used photovoltaicmodule.

The above mentioned method for manufacturing a regenerated photovoltaiccell can be applied to a case of recovering other constituents such asthe transparent front face substrate and the like from the photovoltaicmodule. For example, when recovering a surface glass used as atransparent front face substrate, it can be reused as a photovoltaicmodule surface glass if the adhered substance can be completely removed.When an adhered substance cannot be completely removed or surface glassis broken, it can be recycled as other material by heat melting and thelike. In this case, the adhering amount to the surface glass is smalleras compared with conventional technologies, therefore, recycle cost canbe decreased.

D. Method for Manufacturing Regenerated Transparent Front Face Substrate

The method for manufacturing a regenerated transparent front facesubstrate of the present invention is a method for manufacturing aregenerated transparent front face substrate, wherein a regeneratedtransparent front face substrate is obtained from the above mentionedphotovoltaic module, comprising:

-   -   a heating process of heating the photovoltaic module at        temperatures not lower than the softening temperature of a        thermoplastic resin which is a constituent material of the        separable layer;    -   a separating process of peeling the separable layer, plasticized        by heating, to separate the transparent front face substrate;        and    -   a removing process of removing the encapsulant layer adhered to        the transparent front face substrate. The each process will be        explained below.        1. Heating Process

In the heating process, by heating the photovoltaic module attemperatures not lower than the softening temperature of thethermoplastic resin which is a constituent material of the separablelayer, the separable layer can be easily peeled. The heating method andheating temperature are the same as described in the column of “C.Method for manufacturing regenerated photovoltaic cell”, therefore,description thereof is omitted.

2. Separating Process

In the separating process, the separable layer plasticized by heating inthe above mentioned heating process is peeled to separate thetransparent front face substrate. The separating method is notparticularly limited as long as the transparent front face substrate isnot damaged.

Specifically, methods of using a separating means, method of applyingshearing stress and the like described in the above mentioned column of“C. Method for manufacturing regenerated photovoltaic cell” can belisted.

3. Removing Process

In the removing process, the encapsulant layer adhered to thetransparent front face substrate is removed. The removing method can becarried out by physical cleaning, chemical cleaning or a combinationthereof like in the column of “C. Method for manufacturing regeneratedphotovoltaic cell”. Specifically, since these are the same as describedabove, description thereof is omitted.

After removal of the encapsulant layer, if necessary, cleaning withalcohol and the like is conducted. And the regenerated transparent frontface substrate can be easily manufactured from the used photovoltaicmodule.

E. Method for Reutilizing Photovoltaic Module

Finally, the method for reutilizing a photovoltaic module of the presentinvention will be explained. The method for reutilizing a photovoltaicmodule of the present invention is a method for reutilizing aphotovoltaic module in which a member is reutilized from thephotovoltaic module described in the column of “B. Photovoltaic module”,comprising:

-   -   a heating process of heating the photovoltaic module at        temperatures not lower than the softening temperature of a        thermoplastic resin which is a constituent material of the        separable layer; and    -   a separating process of peeling the separable layer plasticized        by heating to separate the transparent front face substrate.

In the method for reutilizing the photovoltaic module of the presentinvention, for example, members such as a photovoltaic cell contained inthe photovoltaic module, which is determined to be defective inprocessing a photovoltaic module, or members such as the photovoltaiccell of the photovoltaic module recovered after use, and the like can bereutilized (recycle or reuse), this being advantageous from thestandpoint of cost, additionally, being suitable in view of globalenvironments.

As the photovoltaic module subjected to the method for reutilizing thephotovoltaic module of the present invention, as described above, thephotovoltaic module determined to be defective in the process ofmanufacturing the photovoltaic module, and the photovoltaic modulerecovered after use can be listed.

In the present invention, a heating process and separating process areperformed on such the photovoltaic module, and these heating process andseparating process are the same as described in the above mentioned “C.Method for manufacturing regenerated photovoltaic cell” or the abovementioned “D. Method for manufacturing regenerated transparent frontface substrate”, therefore, description thereof is omitted.

In the present invention, it is preferable that the rear face protectingsheet separating process is conducted simultaneously in the abovementioned separating process.

The reason for this is that, for example, when a material generating aharmful gas by heating such as a fluorine-based resin and the like isused as the rear face protecting sheet, by separating the rear faceprotecting sheet from the photovoltaic module in the rear faceprotecting sheet separating process, generation of a harmful gas byheating the rear face protecting sheet when reutilizing the photovoltaicmodule can be prevented, consequently, environmental load can bereduced.

Separation of the rear face protecting sheet may be conductedsimultaneously with separation of the above mentioned photovoltaic cellor transparent front face substrate, or may be conducted beforeseparation of these members.

In the present invention, the treatment after the separating processdiffers depending on whether the member is used as itis (reuse) or themember is used as a material (recycle). In the case of reusing, when themember is, for example, the photovoltaic cell or transparent front facesubstrate, the members is reused by the treating methods described inthe above mentioned “c. Method for manufacturing regeneratedphotovoltaic cell” or the above mentioned “D. Method for manufacturingregenerated transparent front face substrate”. On the other hand, in thecase of recycling, the member is recycled by a recycling methoddescribed later.

Thus, there are a case in which whether the members are reused orrecycled is determined at a stage of the photovoltaic module, and a casein which it is determined after the above mentioned separating process,depending on the state of the member constituting the photovoltaicmodule such as photovoltaic cell, transparent front face substrate andthe like.

(Recycling Method)

In the method for reutilizing the photovoltaic module of the presentinvention, a method for recycling the photovoltaic cell and transparentfront face substrate, among the members of the photovoltaic module, willbe explained.

1. Photovoltaic Cell

When the element is damaged or the like, after the separating process,the element is recycled for uses other than the photovoltaic cell, withor without conducting the above mentioned removing process.

Specifically, the member is re-melted to reform a Si ingot and recycled,or when impurities are contained in large proportion in Si, the memberis used for other uses.

2. Transparent Front Face Substrate

Also in this case, the member is used for uses other than thetransparent front face substrate, with or without conducting the abovementioned removing process, after the separating process. Specifically,by a method such as, the member is recovered as a glass raw material(cullet) and melted to reform a plate glass.

The present invention is not limited to the above mentioned embodiments.The above mentioned embodiments are only example, and any embodimentshaving substantially the same constitution as the technological ideadescribed in claims of the present invention and performing the sameaction effect are included in the technological range of the presentinvention.

EXAMPLES

The following examples will further illustrate the present inventionspecifically.

Example 1 (1) Production of Encapsulant Layer

100 parts by weight of a straight chain low density polyethylene havinga Vicat softening temperature, measured based on JIS standard K7206(hereinafter, referred to as Vicat softening temperature), of 80° C., amelting temperature of 90° C., a melt mass flow rate (hereinafter,referred to as MFR) of 2 g/10 min at 190° C. and a density of 0.898g/cm³, 2.0 parts by weight of vinyltrimethoxysilane and 0.1 part byweight of a free radical generator (t-butyl-peroxy isobutyrate) weremixed and graft-polymerized at a melt stirring temperature of 200° C. tocause silane modification, manufacturing a silane-modified straightchain low density polyethylene.

3.75 parts by weight of a hindered amine-based photo-stabilizer, 3.75parts by weight of a benzotriazole-based ultraviolet absorber and 0.5parts by weight of a phosphorus-based thermal-stabilizer were mixedbased in 100 parts by weight of the straight chain low densitypolyethylene and they were melt-processed to obtain a master batch.

To 20 parts by weight of the above mentioned silane-modified straightchain low density polyethylene having a silane modification ratio of0.3%, 80 parts by weight of a straight chain low density polyethylenehaving a Vicat softening temperature of 70° C., a melting temperature of90° C., a MFR of 3.5 g/10 min at 190° C. and a density of 0.900 g/cm³and 5 parts by weight of the above mentioned master batch were added andmixed. And by using a film molding machine having a 150 mmφ extruder anda 1000 width T dice, formed a film having a thickness of 400 μm at aresin temperature of 230° C. and a casting speed of 4 m/min.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount of the resulting film was 600 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, laminating a glassplate having a thickness of 3 mm (transparent front face substrate), anencapsulant layer having a thickness of 400 μm, a photovoltaic cellformed of polycrystalline silicon, an encapsulant layer having athickness of 400 μm and a laminated sheet composed of a polyvinylfluoride-based resin sheet (PVF) having a thickness of 38 μm, aluminumfoil having a thickness of 30 μm and a polyvinyl fluoride-based resinsheet (PVF) having a thickness of 38 μm as, a rear face protectingsheet, in this order, the photovoltaic module of the present inventionwas manufactured by adhering under press at 150° C. for 15 minutes in avacuum laminator for production of a photovoltaic module, with thesurface of the photovoltaic cell facing up. The encapsulant layer wascut out from the resulting photovoltaic module and its gel fraction wasmeasured to be 0%.

Example 2

The same silane-modified straight chain low density polyethylene as inExample 1 was manufactured, and the same master batch as in Example 1was manufactured.

100 parts by weight of the above mentioned silane-modified straightchain low density polyethylene and 5 parts by weight of the abovementioned waster batch were mixed, and a film of 400 μm was formed inthe same manner as in Example 1.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 3000 ppm.

A photovoltaic module was manufactured in the same manner as inExample 1. The encapsulant layer was cut out from the resultingphotovoltaic module, and its gel fraction was measured to be 0%.

Example 3

The same silane-modified straight chain low density polyethylene as inExample 1 was manufactured, and the same master batch as in Example 1was manufactured.

1. Separable Layer (Outer Layer)

To 20 parts by weight of the above mentioned silane-modified straightchain low density polyethylene, 80 parts by weight of a straight chainlow density polyethylene having a Vicat softening temperature of 70° C.,a melting temperature of 90° C., a MFR of 3.5 g/10 min at 190° C. and adensity of 0.900 g/cm³ and 5 parts by weight of the above mentionedmaster batch were added and mixed.

2. Filling Layer (Inner Layer)

A straight chain low density polyethylene, having a Vicat softeningtemperature of 75° C., a melting temperature of 100° C., a MFR of 3.5g/10 min at 190° C. and a density of 0.902 g/cm³, was used.

The above mentioned separable layer and filling layer were laminated inthe order of separable layer, filling layer and separable layer. Thefilm thickness ratio was 1:6:1. In manufacturing, a film molding machinehaving a 150 mmφ, 50 mmφ multi-layered extruder and a 1000 width T dicewas used, and a multi-layered film having a thickness of 400 μm wasformed at a resin temperature of 230° C. and a casting speed of 4 m/min.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting separable layer was 600 ppm.

A photovoltaic module was manufactured in the same manner as inExample 1. The encapsulant layer was cut out from the resultingphotovoltaic module, and its gel fraction was measured to be 0%.

Example 4

The same silane-modified straight chain low density polyethylene as inExample 1 was manufactured, and the same master batch as in Example 1was manufactured.

1. Separable Layer (Outer Layer)

100 parts by weight of the above mentioned silane-modified straightchain low density polyethylene and 5 parts by weight of the abovementioned master batch were added and mixed.

2. Filling Layer (Inner Layer)

The same filling layer as in Example 3 was used.

A multi-layered film was formed in the same manner as in Example 3.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting separable layer was 3000 ppm.

A photovoltaic module was manufactured in the same manner as inExample 1. The encapsulant layer was cut out from the resultingphotovoltaic module, and its gel fraction was measured to be 0%.

Example 5

The same silane-modified straight chain low density polyethylene as inExample 1 was manufactured, and the same master batch as in Example 1was manufactured.

1. Separable Layer (Outer Layer)

The same separable layer as in Example 3 was used.

2. Filling Layer (Inner Layer)

100 parts by weight of a straight chain low density polyethylene havinga Vicat softening temperature of 75° C., a melting temperature of 100°C., a MFR of 3.5 g/10 min at 190° C. and a density of 0.902 g/cm³ and 5parts by weight of the above-mentioned master batch were added andmixed.

A multi-layered film was formed in the same manner as in Example 3.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting separable layer was 600 ppm.

A photovoltaic module was manufactured in the same manner as inExample 1. The encapsulant layer was cut out from the resultingphotovoltaic module, and its gel traction was measured to be 0%.

Example 6

The same silane-modified straight chain low density polyethylene as inExample 1 was manufactured, and the same master batch as in Example 1was manufactured.

1. Separable Layer (Outer Layer)

The same separable layer as in Example 3 was used.

2. Filling Layer (Inner Layer)

To 5 parts by weight of the above mentioned silane-modified straightchain low density polyethylene, 95 parts by weight of a straight chainlow density polyethylene having a Vicat softening temperature of 75° C.,a melting temperature of 100° C., a MFR of 3.5 g/10 min at 190° C. and adensity of 0.902 g/cm³ and 5 parts by weight of the above mentionedmaster batch were added and nixed.

A multi-layered film was formed in the same manner as in Example 3.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting separable layer was 600 ppm.

A photovoltaic module was manufactured in the same manner as inExample 1. The encapsulant layer was cut out from the resultingphotovoltaic module, and its gel fraction was measured to be 0%.

Example 7

The same silane-modified straight chain low density polyethylene as inExample 1 was manufactured, and the same master batch as in Example 1was manufactured.

1. Separable Layer (Outer Layer)

A film having a thickness of 50 μm was manufactured in the same manneras in Example 1.

2. Filling Layer (Inner Layer)

An ethylene-vinyl acetate copolymer sheet having a thickness of 300 μmwas used.

Laminating a glass plate having a thickness of 3 mm (transparent frontface substrate), the above mentioned separable layer having a thicknessof 50 μm an ethylene-vinyl acetate copolymer sheet having a thickness of300 μm, the above mentioned separable layer having a thickness of 50 μm,the photovoltaic cell formed of polycrystalline silicon, the abovementioned separable layer having a thickness of 50 μm, an ethylene-vinylacetate copolymer sheet having a thickness of 300 μm, the abovementioned separable layer having a thickness of 50 μm, and a laminatedsheet composed of a polyvinyl fluoride-based resin sheet (PVF) having athickness of 38 μm, aluminum foil having a thickness of 30 μm and apolyvinyl fluoride-based resin sheet (PVF) having a thickness of 38 μm,as a rear face protecting sheet, in this order, and the photovoltaicmodule of the present invention was manufactured by adhering under pressat 150° C. for 15 minutes in a vacuum laminator and heating at 150° C.for 15 minutes in a oven for production of a photovoltaic module withthe surface of the photovoltaic cell facing up. The separable layer wascut out from the resulting photovoltaic module, and its gel fraction wasmeasured to be 0%.

Example 8 (1) Manufacture of Encapsulant Layer

100 parts by weight of the same straight chain low density polyethyleneas in Example 1, 0.005 parts by weight of vinyltrimethoxysilane and 0.1parts by weight of a free radical generator (t-butyl-peroxy isobutyrate)were mixed and graft-polymerized at a melt stirring temperature of 200°C. to cause silane modification, manufacturing a silane-modifiedstraight chain low density polyethylene.

To 100 parts by weight of the above mentioned silane-modified straightchain low density polyethylene, 5 parts by weight of the same masterbatch as in Example 1 was added and mixed, and formed into a film havinga thickness of 400 μm by using a film molding machine having a 150 mmφextruder and a 1000 width T dice at a resin temperature of 230° C. and acasting speed of 4 m/min.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 8 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and the sametransparent front face substrate, photovoltaic cell and rear faceprotecting sheet as in Example 1 were laminated in the same manner as inExample 1, and adhered under press at 90° C. for 5 minutes in a vacuumlaminator for manufacture a photovoltaic module with the surface of thephotovoltaic cell facing up, manufacturing the photovoltaic module ofthe present invention. The encapsulant sample was cut out from theresulting photovoltaic module, and its gel fraction was measured to be0%.

Example 9 (1) Manufacture of Encapsulant Layer

To 100 parts by weight of the same silane-modified straight chain lowdensity polyethylene as in Example 1, 5 parts by weight of the samemaster batch as in Example 1 was added and mixed, and formed into a filmhaving a thickness of 400 μm by using a film molding machine having a150 mmφ extruder and a 1000 width T dice at a resin temperature of 230°C. and a casting speed of 4 m/min.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 3000 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and the sametransparent front face substrate, photovoltaic cell and rear faceprotecting sheet as in Example 1 were laminated in the same manner as inExample 1, and adhered under press at 190° C. for 90 minutes in a vacuumlaminator for production of a photovoltaic module with the surface ofthe photovoltaic cell facing up, manufacturing a photovoltaic module ofthe present invention. The encapsulant sample was cut out from theresulting photovoltaic module and its gel fraction was measured to be15%.

Example 10 (1) Manufacture of Encapsulant Layer

100 parts by weight of a straight chain low density polyethylene havinga Vicat softening temperature of 60° C., a melting temperature of 70°C., a MFR of 15 g/10 min at 190° C. and a density of 0.865 g/cm³, 2.0parts by weight of vinyltrimethoxysilane and 0.1 parts by weight of afree radical generator (t-butyl-peroxy isobutyrate) were mixed andgraft-polymerized at a melt stirring temperature of 170° C. to causesilane modification, manufacturing a silane-modified straight chain lowdensity polyethylene.

To 100 parts by weight of the above mentioned silane-modified straightchain low density polyethylene, 5 parts by weight of the same masterbatch as in Example 1 was added and mixed, and formed into a film in thesame manner as in Example 1.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 3000 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and the sametransparent front face substrate, photovoltaic cell and rear faceprotecting sheet as in Example 1 were laminated in the same manner as inExample 1, and adhered under press at 90° C. for 15 minutes in a vacuumlaminator for production of a photovoltaic module with the surface ofthe photovoltaic cell facing up, manufacturing a photovoltaic module ofthe present invention. The encapsulant sample was cut out from theresulting photovoltaic module and its gel fraction was measured to be0%.

Example 11 (1) Manufacture of Encapsulant Layer

100 parts by weight of a high density polyethylene having a Vicatsoftening temperature of 127° C., a melting temperature of 135° C., aMFR of 5 g/10 min at 190° C. and a density of 0.950 g/cm³, 2.0 parts byweight of vinyltrimethoxysilane and 0.1 part by weight of a free radicalgenerator (t-butyl-peroxy isobutyrate) were mixed and graft-polymerizedat a melt stirring temperature of 300° C., manufacturing asilane-modified straight chain low density polyethylene.

To 100 parts by weight of the above mentioned silane-modified straightchain low density polyethylene, 5 parts by weight of the same masterbatch as in Example 1 was added and mixed, and formed into a film havinga thickness of 400 μm by using a film molding machine having a 150 mmφextruder and a 1000 width T dice at a resin temperature of 300° C. and acasting speed of 4 m/min.

Film formation could be conducted without problems. The appearance ofthe resulting film was excellent. The polymerized Si amount in theresulting film was 3000 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and the sametransparent front face substrate, photovoltaic cell and rear faceprotecting sheet as in Example 1 were laminated in the same manner as inExample 1, and adhered under press at 230° C. for 15 minutes in a vacuumlaminator for production of a photovoltaic module with the surface ofthe photovoltaic cell facing up, manufacturing a photovoltaic module ofthe present invention. The encapsulant sample was cut out from theresulting photovoltaic module and its gel fraction was measured to be0%.

Example 12 (1) Manufacture of Encapsulant Layer

100 parts by weight of a straight chain low density polyethylene havinga Vicat softening temperature of 80° C., a melting temperature of 90°C., a MFR of 0.1 g/10 min at 190° C. and a density of 0.900 g/cm³, 2.0parts by weight of vinyltrimethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxy isobutyrate) were mixed andgraft-polymerized at a melt stirring temperature of 200° C. to causesilane modification, manufacturing a silane-modified straight chain lowdensity polyethylene.

To 100 parts by weight of the above mentioned silane-modified straightchain low density polyethylene, 5 parts by weight of the same masterbatch as In Example 1 was added and mixed, and formed into a film havinga thickness of 400 μm by using a film molding machine having a 150 mmφextruder and a 1000 width T dice at a resin temperature of 250° C. and acasting speed of 4 m/min.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 3000 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and the sametransparent front face substrate, photovoltaic cell and rear faceprotecting sheet as in Example 1 were laminated in the same manner as inExample 1, and adhered under press at 150° C. for 60 minutes in a vacuumlaminator for production of a photovoltaic module with the surface ofthe photovoltaic cell facing up, manufacturing a photovoltaic module ofthe present invention. The encapsulant sample was cut out from theresulting photovoltaic module and its gel fraction was measured to be0%.

Example 13 (1) Manufacture of Encapsulant Layer

100 parts by weight of a straight chain low density polyethylene havinga Vicat softening temperature of 80° C., a melting temperature of 90°C., a MFR of 50 g/10 min at 190° C. and a density of 0.880 g/cm³, 2.0parts by weight of vinyltrimethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxy isobutyrate) were mixed andgraft-polymerized at a melt stirring temperature of 200° C.,manufacturing a silane-modified straight chain low density polyethylene.

To 100 parts by weight of the above mentioned silane-modified straightchain low density polyethylene, 5 parts by weight of the same masterbatch as in Example 1 was added and mixed, and formed into a film havinga thickness of 400 μm by using a film molding machine having a 150 mmφextruder and a 1000 width T dice at a resin temperature of 190° C. and acasting speed of 15 m/min.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 3000 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and the sametransparent front face substrate, photovoltaic cell and rear faceprotecting sheet as in Example 1 were laminated in the same manner as inExample 1, and adhered under press at 110° C. for 30 minutes in a vacuumlaminator for production of a photovoltaic module with the surface ofthe photovoltaic cell facing up, manufacturing a photovoltaic module ofthe present invention. The encapsulant sample was cut out from theresulting photovoltaic module and its gel fraction was measured to be0%.

Example 14 (1) Manufacture of Encapsulant Layer

100 parts by weight of a straight chain low density polyethylene havinga Vicat softening temperature of 80° C., a melting temperature of 90°C., a MFR of 2 g/10 min at 190° C. and a density of 0.898 g/cm³, 3.0parts by weight of vinyltrimethoxysilane and 0.1 parts by weight of afree radical generator (t-butyl-peroxy isobutyrate) were mixed andgraft-polymerized at a melt stirring temperature of 200° C.,manufacturing a silane-modified straight chain low density polyethylene.

To 100 parts by weight of the above mentioned silane-modified straightchain low density polyethylene, 0.01 parts by weight of a straight chainlow density polyethylene having a Vicat softening temperature of 70° C.,a melting temperature of 90° C., a MFR of 3.5 g/10 min at 190° C. and adensity of 0.900 g/cm³ and 5 parts by weight of the same master batch asin Example 1 were added and mixed, and formed into a film having athickness of 400 μm by using a film molding machine having a 150 mmφextruder and a 1000 width T dice at a resin temperature of 230° C. and acasting speed of 4 m/min.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 3500 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and a photovoltaicmodule of the present invention was manufactured in the same manner asin Example 1. The encapsulant sample was cut out from the resultingphotovoltaic module and its gel fraction was measured to be 0%.

Example 15 (1) Manufacture of Encapsulant Layer

A film having a polymerized Si amount of 3500 ppm was manufactured inthe same manner as in Example 14.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and the sametransparent front face substrate, photovoltaic cell and rear faceprotecting sheet as in Example 1 were laminated in the same manner as inExample 1, and adhered under press at 230° C. for 60 minutes in a vacuumlaminator for production of a photovoltaic module with the surface ofthe photovoltaic cell facing up, manufacturing a photovoltaic module ofthe present invention. The encapsulant sample was cut out from theresulting photovoltaic nodule and its gel fraction was measured to be30%.

Example 16 (1) Manufacture of Encapsulant Layer

To 20 parts by weight of the same silane-modified straight chain lowdensity polyethylene as in Example 1, 80 parts by weight of the samestraight chain low density polyethylene as in Example 1 and 5 parts byweight of the same master batch as in Example 1 were added and mixed,and formed into a film having a thickness of 10 μm by using a filmmolding machine having a 150 mmφ extruder and a 1000 width T dice at aresin temperature of 230° C. and a casting speed of 18 m/min.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 600 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and a photovoltaicmodule of the present invention was manufactured in the same manner asin Example 1. The encapsulant sample was cut out from the resultingphotovoltaic module and its gel fraction was measured to be 0%.

Example 17 (1) Manufacture of Encapsulant Layer

To 20 parts by weight of the same silane-modified straight chain lowdensity polyethylene as in Example 1, 80 parts by weight of the samestraight chain low density polyethylene as in Example 1 and 5 parts byweight of the same master batch as in Example 1 were added and mixed,and formed into a film having a thickness of 2000 μm by using a filmmolding machine having a 150 mmφ extruder and a 1000 width T dice at aresin temperature of 230° C. and a casting speed of 1 m/min.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 600 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and a photovoltaicmodule of the present invention was manufactured in the same manner asin Example 1. The encapsulant sample was cut out from the resultingphotovoltaic module and its gel fraction was measured to be 0%.

Example 18 (1) Manufacture of Encapsulant Layer

To 100 parts by weight of the same silane-modified straight chain lowdensity polyethylene as in Example 1, 9900 parts by weight of the samestraight chain low density polyethylene as in Example 1 and 5 parts byweight of the same master batch as in Example 1 were added and mixed,and formed into a film in the same manner as in Example 1.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 30 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and a photovoltaicmodule of the present invention was manufactured in the same manner asin Example 1. The encapsulant sample was cut out from the resultingphotovoltaic module and its gel fraction was measured to be 0%.

Comparative Example 1

The same procedure as in Example 1 was conducted excepting that asilane-modified straight chain low density polyethylene was not used.

Comparative Example 2

A glass plate having a thickness of 3 mm was used as a transparent frontface substrate for a photovoltaic module, and on one surface thereof, anethylene-vinyl acetate copolymer sheet having a thickness of 400 μm, aphotovoltaic cell formed of polycrystalline silicon, an ethylene-vinylacetate copolymer sheet having a thickness of 400 μm, and a laminatedsheet composed of a polyvinyl fluoride-based resin sheet (PVF) having athickness of 38 μm, aluminum foil having a thickness of 30 μm and apolyvinyl fluoride-based resin sheet (PVF) having a thickness of 38 μmas a rear face protecting sheet, were laminated and adhered under pressat 150° C. for 15 minutes in a laminator for production of aphotovoltaic module with the surface of the photovoltaic cell facing up,then, heated in an oven of 150° C. for 15 minutes, to manufacture aphotovoltaic nodule.

The encapsulant sample was cut out from the resulting photovoltaicmodule and its gel fraction was measured to be 94%.

Comparative Example 3 (1) Manufacture of Encapsulant Layer

100 parts by weight of the same straight chain low density polyethyleneas in Example 1, 0.0007 parts by weight of vinyltrimethoxysilane and 0.1parts by weight of a free radical generator (t-butyl-peroxy isobutyrate)were mixed and graft-polymerized at a melt stirring temperature of 200°C., manufacturing a silane-modified straight chain low densitypolyethylene.

To 100 parts by weight of the above mentioned silane-modified straightchain low density polyethylene, 5 parts by weight of the same masterbatch as in Example 1 was added and mixed, and formed into a film havinga thickness of 400 μm by using a film molding machine having a 150 mmφextruder and a 1000 width T dice at a resin temperature of 230° C. and acasting speed of 4 m/min.

Film formation could be conducted without problems. The appearance andtotal ray transmittance of the resulting film were excellent. Thepolymerized Si amount in the resulting film was 1 ppm.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and the sametransparent front face substrate, photovoltaic cell and rear faceprotecting sheet as in Example 1 were laminated in the sane manner as inExample 1, and adhered under press at 150° C. for 15 minutes in a vacuumlaminator for production of a photovoltaic module with the surface ofthe photovoltaic cell facing up, manufacturing a photovoltaic module ofthe present invention. The encapsulant sample was cut out from theresulting photovoltaic module and its gel fraction was measured to be0%.

Comparative Example 4 (1) Manufacture of Encapsulant Layer

A film was manufactured in the same manner as in Example 12 except that100 parts by weight of a straight chain low density polyethylene havinga MFR of 0.01 g/10 min at 190° C. was used.

Film formation could be conducted though it was extremely difficult. Theappearance and total ray transmittance of the resulting film wereexcellent. The polymerized Si amount in the resulting film was 3000 ppm.

(2) Manufacture of Photovoltaic Module

A photovoltaic module was manufactured in the same manner as in Example12 using the film obtained above.

Comparative Example 5 (1) Manufacture of Encapsulant Layer

A film was manufactured in the same manner as in Example 13 except that100 parts by weight of a straight chain low density polyethylene havinga MFR of 60 g/10 min at 190° C. was used.

(2) Manufacture of Photovoltaic Module

A photovoltaic module was manufactured in the same manner as in Example13 using the film obtained above. However, flow ability in moduleformation was high, consequently, constituents came into mutual contactand the cell was damaged, namely, module formation was impossible.

Comparative Example 6 (1) Manufacture of Encapsulant Layer

20 parts by weight of the same silane-modified straight chain lowdensity polyethylene as in Example 1, 80 parts by weight of the samestraight chain low density polyethylene as in Example 1, 5 parts byweight of the same master batch as in Example 1 and 5 parts by weight ofa cross-linking agent were mixed, and a film having a polymerized Siamount of 3000 ppm was manufactured.

(2) Manufacture of Photovoltaic Module

The resulting film was used as an encapsulant layer, and a photovoltaicmodule of the present invention was manufactured in the same manner asin Example 1. The encapsulant sample was cut out from the resultingphotovoltaic module and its gel fraction was measured to be 32%.

(Evaluation of Property)

The encapsulant layer s used in the photovoltaic modules obtained inExamples 1 to 18 and Comparative Examples 1 to 4 and 6 were subjected tothe following tests.

(1) Measurement of Total Ray Transmittance

The total ray transmittance (%) of the encapsulant layer s used in thephotovoltaic modules obtained in Examples 1 to 18 and ComparativeExamples 1 to 4 and 6 was measured by a color computer. Specifically,the above mentioned encapsulant layer for photovoltaic module sheet wassandwiched in between ethylenetetrafluoroethylene copolymer films(manufactured by Asahi Glass Co., Ltd., trade name: AFLEX 100N), andthey were adhered under press at 150° C. for 15 minutes by a vacuumlaminator for production of a photovoltaic module, then, the abovementioned ethylenetetrafluoroethylene copolymer films were peeled, andonly the above mentioned encapsulant layer for photovoltaic module sheetheated was subjected to measurement.

(2) Measurement of Adherence of Transparent Front Face Substrate

The peeling strength (N/15 mm width) between an encapsulant layer and atransparent front face substrate at room temperature (25° C.) directlyafter manufacture of the photovoltaic modules obtained in Examples 1 to18 and Comparative Examples 1 to 4 and 6 and the peeling strength afterbeing left for 1000 hours under high temperature and high humidityconditions of 85° C. and 85% was measured.

(3) Measurement of Adherence of Photovoltaic Cell

The peeling strength (N/15 mm width) between an encapsulant layer and aphotovoltaic cell formed of polycrystalline silicon at room temperature(25° C.), after the photovoltaic modules obtained in Examples 1 to 18and Comparative Examples 1 to 4 and 6 were left for 1000 hours underhigh temperature and high humidity conditions of 85° C. and 85%, wasmeasured.

(4) Measurement of Output Maintenance Factor of Photoelectronic Power

The photovoltaic modules obtained in Examples 1 to 18 and ComparativeExamples 1 to 4 and 6 were subjected to an environmental test accordingto JIS standard C8917, and output of photoelectronic power was measuredbefore and after the test and evaluated in comparison.

The results of measurement of the above mentioned test are shown inTable 1.

TABLE 1 Adherence of transparent Adherence front face substrate ofphoto- Output Total ray (N/15 mm width) voltaic cell maintenancetransmit- (directly after (after (N/15 mm factor tance (%) production)being left) width) (%) Example 1  95 65 45 42 98 Example 2  95 51 31 3597 Example 3  93 64 44 40 98 Example 4  94 53 33 37 96 Example 5  93 5030 36 96 Example 8  93 49 29 34 96 Example 7  93 53 33 35 97 Example 8 94 1 0.5 0.8 80 Example 9  95 150 140 60 92 Example 10 98 51 3 32 82Example 11 70 51 30 38 96 Example 12 93 50 33 35 96 Example 13 98 49 538 85 Example 14 92 50 30 34 90 Example 15 93 110 80 55 95 Example 16 9545 28 31 80 Example 17 92 90 50 50 95 Example 18 94 60 35 40 96Comparative 92 0 0 0 0 Example 1 Comparative 90 47 27 33 95 Example 2Comparative 91 0.1 0.1 0.1 65 Example 3 Comparative 93 50 33 35 96Example 4 Comparative — — — — — Example 5 Comparative 95 65 45 42 98Example 6

As apparent from measurement results shown in Table 1, the total raytransmittance of the encapsulant layer s used in the photovoltaicmodules of Examples 1 to 18 was excellent. The peeling strength of thephotovoltaic modules of Examples 1 to 18, at room temperature (25° C.),of a transparent front face substrate and a photovoltaic cell was alsoexcellent, and the output maintenance factor of photoelectronic powerwas high.

In contrast, in Comparative Example 1, a silane-modified straight chainlow density polyethylene was not used in an encapsulant layer,consequently, close adhesion with a transparent front face substrate anda photovoltaic cell was impossible and a photovoltaic module could notbe manufactured. In Comparative Example 3, adhesion strength was weak,and a sufficient output maintenance factor as a photovoltaic modulecould not be maintained.

(Regeneration Test)

For Examples 1 to 18 and Comparative Examples 2, 4 and 6, reutilizeability of the transparent front face substrate and the photovoltaiccell was evaluated based on whether the removal of the encapsulant layeris possible or not.

Removal of the encapsulant layer was conducted according to thefollowing method.

1. First Method

The resulting photovoltaic module was placed in an oven of 200° C. Fiveminutes after, the photovoltaic module was removed out of the oven, andseparated into a transparent front face substrate, photovoltaic cell andrear face protecting sheet to which encapsulant layers plasticized byheating adhered respectively. The separated transparent front facesubstrate and photovoltaic cell carrying adhered encapsulant layers wereplaced on a retaining table, and soy oil heated at 200° C. was flown sothat the oil will be in touch with the surface to which the encapsulantlayer is adhered, and the encapsulant layer s were removed from thetransparent front face substrate and the photovoltaic cell.

2. Second Method

The resulting photovoltaic module was placed in an oven of 200° C. Fiveminutes after, the photovoltaic module was removed out of the oven, andseparated into a transparent front face substrate, photovoltaic cell andrear face protecting sheet to which encapsulant layers plasticized byheating adhered respectively. The separated transparent front facesubstrate and photovoltaic cell carrying adhered encapsulant layers weresubjected to a shot blast method under a 200° C. atmosphere andencapsulant layers were removed from the transparent front facesubstrate and the photovoltaic cell.

3. Third Method

The resulting photovoltaic module was placed and heated on a hot plateof 200° C. Seven minutes after, the photovoltaic module was separatedinto a transparent front face substrate, photovoltaic cell and rear faceprotecting sheet to which encapsulant layers plasticized by heatingadhered respectively. The separated transparent front face substrate andphotovoltaic cell carrying adhered encapsulant layers were again placedon a hot plate, and encapsulant layers were wiped off with a cloth.

4. Fourth Method

The resulting photovoltaic module was heated in a silicon oil bathheated at 180° C. Twenty minutes after, a back cover was peeled from theseparable layer plasticized by heating. Next, a φ0.15 mm wire was putthrough the separable layer, plasticized by heating, between glass andphotovoltaic cell, for separation into a transparent front facesubstrate and photovoltaic cell carrying adhered encapsulant layers. Theseparated transparent front face substrate and photovoltaic cellcarrying adhered encapsulant layers were immersed in a xylene bathheated at 80° C. and left for 24 hours. After being left, thephotovoltaic cell and transparent front face substrate were taken out,and separable layers remaining on the element and glass surface weregently wiped off with a waste cloth.

5. Fifth Method

The resulting photovoltaic module was heated in a silicon oil bathheated at 180° C. Twenty minutes after, a back cover was peeled from theseparable layer plasticized by heating. Next, a φ0.15 mm wire was putthrough the separable layer, plasticized by heating, between glass andphotovoltaic cell, for separation into a transparent front facesubstrate and photovoltaic cell carrying adhered encapsulant layers. Theseparated transparent front face substrate and photovoltaic cellcarrying adhered encapsulant layers were placed on a hot plate of 200°C., and stearic acid was poured on a softened separable layer fordissolution, and the dissolved separable layer was gently wiped of witha waste cloth.

6. Sixth Method

The resulting photovoltaic module was heated in a silicon oil bathheated at 180° C. Twenty minutes after, the rear face protecting sheetwas peeled from the separable layer plasticized by heating. Next, aφ0.15 mm wire was put through the separable layer, plasticized byheating, between the transparent front face substrate and thephotovoltaic cell, for separation into a transparent front facesubstrate and photovoltaic cell carrying adhered encapsulant layers.

The separated transparent front face substrate and photovoltaic cellcarrying adhered encapsulant layers were placed on a hot plate of 200°C., and stearic acid was poured on a softened separable layer, and theencapsulant layer s were removed. Thereafter, the photovoltaic cell andtransparent front face substrate carrying encapsulant layers remainingon the surface were immersed in a xylene bath heated at 80° and left for240 hours, to peel the separable layer from the photovoltaic cell and topeel the separable layer from the transparent front face substrate.

7. Seventh Method

The resulting photovoltaic module was heated in a silicon oil bathheated at 180° C. Twenty minutes after, the rear face protecting sheetwas peeled from the separable layer plasticized by heating. Next, aφ0.15 mm wire was put through the separable layer, plasticized byheating, between the transparent front face substrate and thephotovoltaic cell, for separation into a transparent front facesubstrate and photovoltaic cell carrying adhered encapsulant layers. Theseparated transparent front face substrate and the photovoltaic cellcarrying adhered encapsulant layers were immersed in a xylene bathheated at 80° C. and left for 240 hours. After being left, thephotovoltaic cell and the transparent front face substrate carryingencapsulant layers remaining on the surface were taken out and placed ona hot plate of 200° C., and stearic acid was poured on a softenedseparable layer and the separable layer was gently wiped off with awaste cloth.

8. Eighth Method

The resulting photovoltaic module was heated in a silicon oil bathheated at 190° C. Two minutes after, the rear face protecting sheet waspeeled from the separable layer plasticized by heating. Next, using aseparation device shown in FIG. 2, a φ0.08 mm wire was put through theseparable layer, plasticized by heating, between the transparent frontface substrate and the photovoltaic cell, for separation into atransparent front face substrate and photovoltaic cell carrying adheredencapsulant layers. The photovoltaic cell and the transparent front facesubstrate carrying encapsulant layers remaining on the surface weretaken out and placed on a hot plate of 190° C., and the separable layerwas gently wiped off with a waste cloth.

9. Ninth Method

The resulting photovoltaic module was heated in a silicon oil bathheated at 195° C. Two minutes after, the rear face protecting sheet waspeeled from the separable layer plasticized by heating. Next, using aseparation device shown in FIG. 2, a φ0.08 mm wire was put through theseparable layer, plasticized by heating, between the transparent frontface substrate and the photovoltaic cell, for separation into atransparent front face substrate and photovoltaic cell carrying adheredencapsulant layers. The separated transparent front face substrate andthe photovoltaic cell carrying adhered encapsulant layers were immersedin a xylene bath heated at 80° C. and left for 2 hours. The separablelayers remaining on the surface of the photovoltaic cell and transparentfront face substrate were gently wiped off with a waste cloth.

10. Tenth Method

The resulting photovoltaic module was immersed in a xylene bath heatedat 80° C. and left for 20 hours. After being left, The separable layersremaining on the surface of the photovoltaic cell and transparent frontface substrate were gently wiped off with a waste cloth.

Using the above mentioned ten methods, the surfaces of the transparentfront face substrate and the photovoltaic cell, taken out of thephotovoltaic modules obtained in Examples 1 to 18 and ComparativeExamples 2, 4 and 6, were visually observed to confirm if theencapsulant layer was removed or not. In removal of the encapsulantlayer by the above mentioned methods (separating process and removingprocess), when oil and the like is adhered, cleaning with a solvent suchas isopropyl alcohol and the like was conducted as necessity.

As a result of the above mentioned evaluation, removal of theencapsulant layer from the transparent front face substrate and thephotovoltaic cell was rather difficult in Examples 9, 11, 12 and 15,while in the photovoltaic modules obtained in Examples 1 to 18, removalof the encapsulant layer from the transparent front face substrate andthe photovoltaic cell was possible by any of the above mentioned firstto tenth methods. And the transparent front face substrate and thephotovoltaic cell recovered by removing the encapsulant layer could bereused or recycled.

On the other hand, in the photovoltaic module obtained in ComparativeExample 2, the photovoltaic module could not be disassembled by any ofthe above mentioned first to tenth methods. The transparent front facesubstrate and the photovoltaic cell could not be recovered from thephotovoltaic module and could not be reused or recycled. In ComparativeExample 4, since plasticity after softening was low, removal of theencapsulant layer from the transparent front face substrate and thephotovoltaic cell was extremely difficult so that they could not bereused or recycled. Further, in Comparative Example 6, disassemble ofthe photovoltaic module was extremely difficult so that reusing orrecycling was impossible.

1. An encapsulant layer for photovoltaic module, wherein the encapsulantlayer for photovoltaic module is used in a photovoltaic module formed bylaminating: a transparent front face substrate; a photovoltaic cellcarrying a wiring electrode and a takeoff electrode, and the encapsulantlayer is placed on at least one surface of the photovoltaic cell; and arear face protecting sheet, in this order, wherein the encapsulant layerfor photovoltaic module comprises a separable layer, formed mainly of athermoplastic resin which is a copolymer of a polyethylene forpolymerization and an ethylenically unsaturated silane compound, has agel fraction of 10% or less, has no silanol catalyst added, and has: (a)a peeling strength from the transparent front face substrate, measuredin a 180° peeling test under a 25° C. atmosphere, in a range of 1 N/15mm width to 150 N/15 mm width, (b) a Vicat softening temperature,measured based on JIS standard K7206, in a range of 60° C. to 128° C.,and (c) a melt mass flow rate, measured based on JIS standard K7210, ina range of 0.1 g/10 min to 50 g/10 min, and further wherein (d) anoutput maintenance factor of photoelectronic power, before and after atest measured based on a standard, of the photovoltaic module using theencapsulant layer is in a range of 80% to 100%.
 2. The encapsulant layerfor photovoltaic module according to claim 1, wherein the encapsulantlayer placed in between the transparent front face substrate and thephotovoltaic cell (e) has a total ray transmittance in a range of 70% to100%.
 3. The encapsulant layer for photovoltaic module according toclaim 1, wherein the separable layer is placed so as to contact with theboth surfaces of the photovoltaic cell and the transparent front facesubstrate.
 4. The encapsulant layer for photovoltaic module according toclaim 3, wherein the encapsulant layer is obtained by laminating theseparable layer, a filling layer formed of a resin composition differentfrom that of the separable layer, and the separable layer, in thisorder.
 5. The encapsulant layer for photovoltaic module according toclaim 3, wherein the encapsulant layer is formed only of the separablelayer.
 6. The encapsulant layer for photovoltaic module according toclaim 1, wherein the peeling strength between the encapsulant layer andthe transparent front face substrate, measured in a 180° peeling testunder a 25° C. atmosphere, after the photovoltaic module is left underhigh temperature and high humidity conditions of 85° C. and 85% for 1000hours is in a range of 0.5 N/15 mm width to 140 N/15 mm width.
 7. Theencapsulant layer for photovoltaic module according to claim 1, whereinthe thermoplastic resin further contains a polyethylene for addition. 8.The encapsulant layer for photovoltaic module according to claim 1,wherein the separable layer contains Si (silicon) in an amount of 8 ppmto 3500 ppm in terms of polymerized Si amount.
 9. The encapsulant layerfor photovoltaic module according to claim 1, wherein the separablelayer further contains at least one additive selected from the groupconsisting of photo-stabilizers, ultraviolet absorbers,thermo-stabilizers and antioxidants.
 10. A photovoltaic modulecomprising the encapsulant layer for photovoltaic module, according toclaim 1, placed on at least one surface of a photovoltaic cell.
 11. Amethod for manufacturing a regenerated photovoltaic cell, wherein aregenerated photovoltaic cell is obtained from the photovoltaic moduleaccording to claim 10, comprising: a heating process of heating thephotovoltaic module at temperatures not lower than the softeningtemperature of a thermoplastic resin which is a constituent material ofthe separable layer; a separating process of peeling the separablelayer, plasticized by heating, to separate the photovoltaic cell; andremoving process of removing the encapsulant layer adhered to thephotovoltaic cell.
 12. The method for manufacturing a regeneratedphotovoltaic cell according to claim 11, wherein the removing process iscarried out by physical cleaning of physically removing the encapsulantlayer, chemical cleaning of chemically removing the encapsulant layer,or a combination thereof.
 13. A method for manufacturing a regeneratedtransparent front face substrate, wherein a regenerated transparentfront face substrate is obtained from the photovoltaic module accordingto claim 10, comprising: a heating process of heating the photovoltaicmodule at temperatures not lower than the softening temperature of athermoplastic resin which is a constituent material of the separablelayer; a separating process of peeling the separable layer, plasticizedby heating, to separate the transparent front face substrate; and aremoving process of removing the encapsulant layer adhered to thetransparent front face substrate.
 14. The method for manufacturing aregenerated transparent front face substrate according to claim 13,wherein the removing process is carried out by physical cleaning ofphysically removing the encapsulant layer, chemical cleaning ofchemically removing the encapsulant layer, or a combination thereof. 15.A method for reutilizing a photovoltaic module, wherein a component fromthe photovoltaic module according to claim 10 is reutilized, comprising:a heating process of heating the photovoltaic module at temperatures notlower than the softening temperature of a thermoplastic resin which is aconstituent material of the separable layer; and a separating process ofpeeling the separable layer plasticized by heating to separate thetransparent front face substrate.
 16. The method for reutilizing thephotovoltaic module according to claim 15, wherein the separatingprocess comprises a rear face protecting sheet separating process ofseparating a rear face protecting sheet from the photovoltaic module.17. The encapsulant layer for photovoltaic module according to claim 1,wherein the copolymer of the polyethylene for polymerization and theethylenically unsaturated silane compound is a graft copolymer.